The long-term objective of this research is to identify the knowledge-based and capacity-based factors which are associated with improvement, maintenance, and decline in effective cognitive functioning in healthy older adults. The first proposed experiment seeks to clarify the nature of the effects of prior domain-related knowledge on adult age differences in summarizing the information available in text materials in the target domain. Proposed experiments 2, 3, and 4 examine age-related and skill-related differences in searching for target items in "visually-rich" displays. It is expected that the beneficial effects of skill-related knowledge on the cognitive performance of older adults will be demonstrated by contrasting the visual search performance of older adults under domain-specific and domain-general visual display formats. Adult age differences in the effects of domain-related skill on reducing the capacity demands of visual search are assessed using a dual-task methodology (comparing Experiments 3 and 5). Older adults are expected to show capacity-based limitations in domain-general visual search but not in domain-specific search, and they are expected to show less transfer of the domain-specific skills of visual search to the task of identifying and summarizing the main points of text materials in the target domain.